The Toronto stock exchange opened considerably lower Tuesday morning as largest potash producers stocks tumbled because of Russian-based Uralkali (LON: URALL) decision of cancelling a European marketing group, which controls roughly 43% of global exports.

Canadian exporting and marketing firm (Canpotex) members were among the worst hitten. Saskatoon-based PotashCorp. (TSX:POT), the country’s largest potash producer, was down almost 21% in Toronto and the same in New York, at 10:30 ET.

US based Mosaic (NYSE:MOS) also took a major hit, dropping 23% to $40.59, while Agrium (TSX:AGU) saw its stock dive 8.7% to $83.49.

The blood bath was triggered by competitor Uralkali’s announcement that it is stopping its export sales through the Belarusian Potash Company to direct all export volumes through its own Uralkali Trading. The decision is likely to undercut competitors' prices for the fertilizer.

CEO Vladislav Baumgertner his company has supported a united sales network but that has been upset by a Belarusian presidential decree in December and sales by Belaruskali outside the marketing partnership.

"Unfortunately, we should state that our cooperation with our Belarusian partners within BPC framework has come to a deadlock," Baumgertner said in a statement.